![]() “And that energy can create under-ice oceans, maybe even habitable zones. “The same gravity that causes all these weird phenomena that we’re seeing on these little moons causes energy to be pumped into some of the larger ones,” says Terrile. Understanding Pan and Atlas may be key to understanding gravity’s role in all of Saturn’s moons. “It may also be some kind of gravitational tidal effect from being near all this ring material,” says Terrile. The dominant theory for how the ridges form is that because the moons’ diameters are so much larger than the ring’s thickness, they gather material along their equators as they plow through stray ring particles. The two moons are approximately the same size, but Pan is embedded within a ring, and Atlas is along the outer edge. “What is especially interesting is the extent to which the soft material seems to bury and mute any crisp-looking topographic features even on the central ‘core’ structure,” says Paul Helfenstein at Cornell University in Ithaca, New York, who helped plan the flyby.Īnother moon, Pan, also has an equatorial ridge, but another recent flyby showed its ridge is rough with tension cracks and craters. It Turns Out that Our Moon Once Had an Atmosphere. Ingenieros Japoneses quieren Construir un Hábitat de Gravedad Artificial en la Luna. “It looks like it’s covered in some kind of fluffy material.” Físico de la Defensa de Estados Unidos Habla sobre lo que Realmente está Sucediendo en la Luna. “It looks more subdued than I expected,” Terrile says. We already knew Atlas has a UFO-like ridge around its equator, but surprisingly, the new images show that ridge is smooth. “This is a really interesting kind of dynamical dance that these moons do with the ring particles.” But instead, the ring’s shape is held by two other moons, Janus and Epimetheus. “At the time, we thought the satellite was holding out the edge of the A ring,” Terrile says. But Atlas appears to be a shepherd moon that isn’t responsible for shepherding ring particles. Every two weeks, we have to look in the opposite direction to see the Moon, and the ground beneath our feet is then tilted the opposite way as well.Some of Saturn’s moons, called shepherd moons, use their gravity to keep the planet’s famous rings in check. The tilted ramp works the same as the tilted “platform” of the Earth beneath our feet. If you turn around, the horizon appears to tilt the opposite way. In front of you, the horizon looks higher on the right and lower on the left. Earth has a tilt of 23.5 degrees on its axis, which means that when we observe the Moon from Earth, it’s a little like we’re standing sideways on a ramp. 3 Locked Up The Earth and Moon are tidally locked. It goes around the Earth at a distance of about 239,000 miles (385,000 kilometers). The tilt of the Moon’s orbit contributes to this, but it’s mostly due to the tilt of our Earth. The Moon is Earths only natural satellite. We call this motion “libration in latitude.”įinally, the Moon appears to tilt back and forth like a metronome. The 5 degree tilt of the Moon’s orbit also causes it to appear to nod, as though it were saying “yes.” The tilt sometimes brings the Moon above Earth’s northern hemisphere, and sometimes below Earth’s southern hemisphere, allowing us to see slightly more of the northern or southern hemispheres of the Moon. We call this motion “libration in longitude.” When the Moon is farthest from Earth and orbiting at its slowest, its rotation gets a little ahead, and we see a bit more of its western side. When the Moon is at its closest to Earth and moving most quickly along its orbital path, the Moon itself doesn’t rotate quite fast enough to keep entirely the same side facing us, and we get to see a little more of the eastern side of the Moon. ![]() The Moon’s rate of rotation around its own axis, though, always stays the same. Because the Moon's orbit is not perfectly circular, its distance from Earth and its speed in orbit both change slightly throughout the month.
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